1. Field of the Invention
The present invention relates to a semiconductor structure and the manufacturing method thereof, and more particularly, to a method and a semiconductor structure for modifying the spacer to enhance the effect of a stress layer.
2. Description of the Prior Art
As semiconductor processes advance to the very deep sub micron level, how to increase the driving current for MOS transistors has become a critical issue in this field.
To attain higher performance of a semiconductor device, attempts have been made to use a strained silicon (Si) layer for increasing the mobility of electrons or holes. Taking advantage of a stressor is a common way to increase the effect of the MOS transistors. Forming a tensile or a compressive stressor on the substrate and using the MOS transistors to change the band structure of silicon can increase mobility of electrons.